Drill collar for protecting drill string



Nov. 25, 1969 J. B. N. MORRIS DRILL COLLAR FOR PROTECTING DRILL STRING Filed March 21, 1968 .B M L'Z ORNEYS United States Patent 3,480,094 DRILL COLLAR FOR PROTECTING DRILL STRING James B. N. Morris, New Orleans, La. (BO. Box 663, Harvey, La. 70058) Filed Mar. 21, 1968, Ser. No. 714,833 Int. Cl. EZlb 17/00; E21c 9/00; F16c 1 26 US. Cl. 175-325 9 Claims ABSTRACT OF THE DISCLOSURE An improved drill collar having improved shock absorbing and abrasion and heat resisting characteristics is described. The improved drill collar is of a type which can be attached or adhered to drill string or drill pipe to protect the same from abrasion and shock while being used in earth boring operations. The improved drill collar comprises an elastomeric sleeve means which can be adhered or affixed to a drill string, and the exterior surface of the elastomeric sleeve means includes a plurality of closely spaced ceramic elements. The closely spaced ceramic elements are positioned in or on the exterior surface of the elastomeric sleeve means so as to be exposed on the drill collar exterior surface, and the plurality of ceramic elements provides substantially improved abrasion and heat resistant characteristics for the drill collar. The ceramic elements may be made of a porcelain composition, and the elastomeric sleeve means can be of a neoprene rubber composition having a Shore A durometer hardness in the range of approximately 60 to 70.

BACKGROUND AND BRIEF SUMMARY OF THE INVENTION This invention relates to protective devices for drill strings, or drill pipes, and in particular the invention provides for an improved drill collar which can be used with a drill string to protect the drill string from shock, abrasion, and heat during earth boring operations.

In the art of earth boring, as for example in the drilling of oil wells, drill bits and other drilling equipment are attached to the end of a drill string for boring a hole into the earth. Typically, the drill string may comprise a long string of drill pipe which extends from the surface of the earth down into the drill hole or bore which is being formed by a drill bit carried at the bottom end of the drill string. The drill hole may be an open hole during the drilling operations, or a casing may be installed in the drill hole and the drill string can then operate within the casing. When it is desired to bore into the earth, the drill string is rotated and lowered so as to carry out a cutting action by the drill bit into the earth. It is a known problem in the earth boring art that drill strings are subjected to severe shocks, abrasions, and heat during normal drilling operations. For example, a very long drill string will whip about in an earth bore or casing in which it is positioned, and contact of the drill string with the walls of the drill hole or its casing will impart severe shocks and abrasions to the portions of the drill string which make such contact. Additionally, in directional drilling operations, and in operations where the drill string is rotated at relatively high speeds (for example, at 200 rpm. or more), frictional heat becomes a serious problem, and the drill string must be protected from sustained frictional contact with the walls of the drill hole or its casing.

It is known in this art to provide protective devices in the form of collars which can be placed about portions of a drill string to maintain the drill string in a spaced position away from the walls of a casing in a bore. At the present time, it is a common expedient to utilize hard metal drill collars to protect portions of drill strings, but it has been found that even metal drill collars are inadequate for providing full abrasion and heat protection for a drill string which is operating in an uncased bore or in a directional bore. In fact, tool joints, and other portions of drill strings, have been known to melt from frictional heat in directional holes where the drill string has been rotated at approximately 200 r.p.m.s. The problem of friction and high heat becomes even more serious where the bore is uncased and open since portions of the drill string will contact the rough and hard earth into which the hole is being formed, as contrasted with other operations where a drill string is rotated within a casing which is placed in the drill hole as it is being formed. Typical patents illustrating the use of metal or metal covered protectors for drill strings are Huntsinger 2,247,173, June 24, 1941, and Clark 2,259,023, Oct. 14, 1941.

Also, it is known in the art to provide rubber, or other elastomeric material, devices for protecting portions of drill strings, as exemplified by Anderson Patent 2,153,787 of Apr. 11, 1939, and Lane Patent 2,715,552 of Aug. 16, 1955. The use of rubber, or its equivalent, is desirable because of its shock absorbing characteristics, however, it has been found that rubber products deteriorate rather rapidly in normal usage, and therefore, it is necessary to periodically shut down operations to remove and replace deteriorated drill string protectors. In addition, rubber products are easily cut and mechanically disintegrated by abrasion when used in open holes, and this has further limited attempted uses of rubber protectors for drill strings.

The present inventionl solves the problems of the prior art and provides a novel drill collar construction having substantially improved characertistics for resisting shock, abrasion, and heat. All of these charactertistics are especially desirable in deep borings which are directional and which are formed by a high r.m.p. rotation of a drill bit. Such borings subject long drill strings, and their joints, to severe stresses and strains, and continued contact of portions of the drill string with the earth walls of the drill hole result in extreme shocks, abrasions, and heat development during the drilling operation. Even the use of metal drill collars, in such operations, is unsatisfactory because the metal may melt from frictional heat. Also, metal drill collars tend to stiffen a drill string at the points of attachment of the collars to the string, and this may result in a fatiguing of the drill string at the points of drill collar attachment.

The present invention provides for a drill collar having a somewhat flexible and shock absorbing base portion in the form of a resilient sleeve means which can embrace a drill string. The sleeve means of the drill collar may be made of any suitable elastomeric material such as rubber or neoprene, and the sleeve means is affixed to the drill string by mechanical devices or by adhesion with a suitable bon-ding agent. The exterior surface of the elastomeric sleeve means is essentially covered with ceramic elements or chips which are positioned near or on the exterior surface so as to be exposed at or above the exterior surface of the drill collar. The ceramic elements or chips may be of a porcelain composition which has high heat and abrasion resistant characteristics, and the ceramic elements may be either bonded to surface of the elastomeric sleeve means or embedded just below its surface so as to leave portion-s which can be exposed when the drill collar is used in a drilling operation.

It has been found that the novel drill collar of this invention has substantially improved characteristics over any drill collar construction previously known to this art. The improved drill collar resists very high frictional temperatures and will not melt or deteriorate at such high temperatures even where the drill string is operating at high r.p.m.s in a directional open bore. Also, the porcelain elements of the drill collar provide for substantially improved abrasion characteristics for the drill collar, and this reduces friction and disintegration of the entire collar by contact of the collar with the walls of a bore or with the walls of a casing within a bore. However, it is not enough to merely provide a porcelain or ceramic coating on a drill collar since such ceramic materials are extremely brittle and would be fractured and disintegrated upon normal contact with the walls of a bore or a casing. However, the present invention has discovered that a large number of ceramic elements can be placed on the surface of a rubber sleeve without being prematurely fractured or destroyed, and in fact, the elastomeric sleeve provides a sufiiciently resilient support for each ceramic element so as to protect it from shocks of impacts with portions of a drill hole or its casing. In turn, the elastomeric sleeve absorbs shocks which otherwise would be transmitted to the drill string itself, and this reduces stresses and strains on the drill string. Also, contrary to what might be expected, the elastomeric or rubber sleeve portion of the drill collar of this invention does not deteriorate rapidly from exposure to crude petroleum and other earth boring fluids, as has been the experience with rubber or elastomeric protective devices which have been attempted in the past. Apparently, the inclusion of ceramic elements over a substantial portion of the drill collar surfaces reduces exposure of the elastomeric sleeve means to well fluids by a sufficient amount to substantially eliminate the problem of rapid deterioration of flexible drill collars.

Thus, the improved drill collar of the present invention provides for a novel combination of characteristics which have not been achieve-d with prior attempts and prior products. The combined characteristics offer a very useful drill collar device which can be used in all types of earth boring operations, and for the first time, there is provided a long life drill collar which can operate at high speeds and at high temperatures in directional open bores. In addition to all of the advantages discussed above, the improved drill collar of this invention can be easily removed from a bore or a casing if the collar should break down or become stuck in the bore or casing. Unlike prior devices which have required costly retrieval operations to remove a damaged drill collar and drill string from a boring, the present drill collar can be purposely disintegrated by explosive force or by mechanically drilling it out of a stuck position, and retrieval can be accomplished at a reasonably low cost without damage tothe drill string or the drill hole itself.

These and other advantages of the present invention will become more apparent in the detailed discussion which follows, and in the detailed discussion reference will be made to accompanying drawings as described below.

BRIEF DESCRIPTION OF DMWINGS FIGURE 1 is a perspective view, partially cut away, to illustrate the drill collar of this invention;

FIGURE 2 is a cross sectional view of the drill collar of FIGURE 1, as seen from line 22 of FIGURE 1;

FIGURE 3 shows a portion of the FIGURE 2 cross sectional view which is enlarged to illustrate one manner in which ceramic elements may be adhered to the exterior surface of the drill collar of this invention;

FIGURE 4 is an enlarged portion of a cross sectional view, similar to the section of FIGURE 3, and showing a second manner in which ceramic elements may be affixed to an exterior surface of the drill collar; and

FIGURES 5(a) through (c) illustrates examples of several forms of ceramic elements which may be used as a part of the improved drill collar construction of this invention.

4 DETAILED DESCRIPTION OF INVENTION Referring to FIGURE 1, an improved drill collar 10 of this invention is illustrated in a perspective view which is partially cut away to show the relationship of the drill collar to a portion of a drill string 12. Although this specification will make reference to drill strings, it is to be understood that such terminology refers to pipe strings or any other equivalent type structure used with earth boring apparatus (for example sucker rods). The drill string 12 which is illustrated in FIGURE 1 is in the form of a pipe string, and the drill collar 10 may be affixed or adhered directly to a portion of the pipe string or to a pipe segment which can be inserted into a pipe string. It is known, for example, to provide externally threaded connectors at each end of a pipe segment (of the type shown as 12 in FIGURE 1) so that the threaded ends can be received into internally threaded drill pipe sections. However, the important features of the present invention reside in the construction of the drill collar 10, and it is contemplated that the improved drill collar of this invention may be used in any environment where it is desired to protect a member from shock, abrasion, and heat.

The improved drill collar includes an elastomeric sleeve means 14 which makes up a major portion of the drill collar construction, and the elastomeric sleeve means 14 may be manufactured from known rubber, or rubber-like compounds. It has been found that neoprene is very satisfactory for this purpose. The sleeve 14 is illustrated as being cylindrical in form so as to fit about a portion of a drill string 12 (or a pipe section 12 which is designed to be attached into a drill string). Alternatively, the drill collar 10 may be made in halves or segments which can be wrapped around a drill string and fastened thereto at any desired location. The elastomeric sleeve means 14 has an inner surface 16 for contacting the exterior surface of a pipe 12, and it has an exterior surface 18 which contacts the walls of a hole being bored into the earth (or of a casing which has been set into such a hole while a drill string is operating within the casing). Thus, the drill collar 10 is constructed to maintain the drill string 12 in a spaced relationship away from the walls of a drill hole or its casing, and additionally, the drill collar 10 of this invention is designed to absorb shocks and to resist abrasion and heat which might otherwise seriously affect the operation of a drill string within a drill hole.

The elastomeric sleeve means 14 includes in its exterior surface 18 a plurality of closely spaced ceramic elements 20 which are positioned on the exterior surface so as to be exposed to any contact of the surface 18 with walls of a drill hole or its casing. FIGURES 1 through 3 illustrate an embodiment wherein the plurality of closely spaced ceramic elements 20 are adhered to the outside surface of the elastomeric sleeve means 14, and FIGURE 4 illustrates an embodiment wherein the ceramic elements 20 are embedded into the exterior surface 18 of the clastomeric sleeve means 14. In either embodiment, the ceramic elements are positioned so as to protect the elastomeric sleeve means 14, and the drill string 12, from frictional heat and abrasion when the drill collar contacts any portion of a drill hole or its casing.

The ceramic elements 20 may be of any suitable shape or configuration, and several shapes are illustrated in FIGURES 5(a) through (0). FIGURE 5(a) shows a ceramic element or chip which has a square or rectangular configuration, and the edges and corners of the chip can be rounded off, as shown. The elements shown in FIG- URES 5 (b) and (0) provide for a rounded exterior surface which can make contact with portions of a drill hole or casing, and the rounded surfaces reduce abrasion and friction. In addition, it is contemplated that irregular or random shapes and forms of ceramic elements may be included in the composition of an elastomeric sleeve 14 to provide the unusual characteristics which have been achieved by the present invention.

FIGURE 1 illustrates a drill collar which has been constructed with a large number of closely spaced ceramic elements 20 of the type shown in FIGURE 5(a). The spacings which are shown in the drawings are exaggerated for clarity, but generally, a large number 'of relatively small ceramic elements or chips 20 are positioned about the exterior surface of the elastomeric sleeve means 14. By providing such a surface configuration for the drill collar 10, the relatively soft and resilient material of the elastomeric sleeve means 14 is protected from rapid mechanical disintegration or chemical deterioration. In addition, the ceramic elements 20 are of a composition which can withstand very high temperatures, and they are sufificiently strong and hard to withstand physical abrasion. By forming the surface of the drill collar from a large number of such ceramic elements, it has been found that each element is sufiiciently supported andprotected by the underlying resilient sleeve means 14 to prevent rapid fracturing or disintegration of the very hard and brittle ceramic surface of the drill collar. Thus, there is provided a novel combination of materials in a novel construction which results in substantially improved, and even unexpected, characteristics of long life and performance for drill collars and similar protective devices.

In the embodiment of FIGURES 1 through 3, the plurality of ceramic elements 20 are bonded or adhered to the outside surface of the elastomeric sleeve means 14. Suitable adhesives and other bonding agents are known for effecting a secure bonding of each ceramic element 20 to an elastomeric sleeve means 14 of the type contemplated by this invention.

In the embodiment illustrated in FIGURE 4, the ceramic elements 20 are embedded in the elastomeric sleeve means 14 so as to include a plurality of such elements at or near the surface 18 of the drill collar. The ceramic elements 20 which are embedded in the elastomeric sleeve may be of any shape or configuration, as with the FIGURE 1 embodiment, but a preferred configuration is shown in FIGURE 4. In the FIGURE 4 embodiment, each ceramic element 20 is of the type shown in either FIGURES 5( b) or (c), and the elements are embedded into the surface 18 of the elastomeric sleeve so as to present curved surfaces towards the exterior of the sleeve means. In this way, the rotating drill collar will contact portions of the drill hole or its casing, and almost all mechanical shocks or abrasions will be received on tangents to the plurality of curved surfaces of the ceramic elements 20. In addition, the use of ceramic elements which are substantially hemispherical in shape, as in FIGURE 5(1)), or which have rounded exterior surfaces generally, provides for greater and greater exposure of a ceramic surface as the exterior surface of the drill collar is worn away by continued use. It can be seen in FIGURE 4 that initially very little of the curved ceramic elements 20 are exposed to actual contact with a drill hole or its casing, but as the drill collar 10 wears down from continued use, a greater area of ceramic surface will be exposed to all mechanical shocks and abrasions and to frictional heat which is produced by the contact of the rotating drill collar with portions of the drill hole or its casing. The ceramic elements 20 of the FIGURE 4 embodiment may be included in the elastomeric sleeve means while it is being molded or formed, or the individual elements 20 may be bonded or adhered into pockets or recesses which are formed into a surface 18 of an elastomeric sleeve means 14.

As an example of a construction which has been manufactured in accordance with the present invention, a drill collar 10 has been produced from a combination of a neoprene elastomeric sleeve 14 and porcelain ceramic elements 20. Considering the configuration shown in FIG URE 1, the drill string pipe 12 may have an outside di ameter of 5 inches, and the drill collar 10 may have an overall length of 9 inches and an outside diameter of approximately 6% inches. A plurality of ceramic elements of the type shown in FIGURE 5(a) may be bonded to the exterior surface 18 of the neoprene sleeve 14 so as to cover the surface in the manner shown in FIGURE 1. Each of the ceramic elements 20 may have a thickness of approximately inch, and a length and width of A inch. The individual elements 20, of the type shown in FIGURE 5(a), may be perfectly fiat or they may have exterior surfaces 22 which are slightly curved so as to form an overall curved surface which is concentric with the exterior surface 18 of the elastomeric sleeve 14. The edges of the individual porcelain elements 20 may be rounded off in any suitable way, such as by tumbling the elements after they have been manufactured. In the example of construction shown in FIGURE 1, the individual porcelain elements 20 may be spaced approximately inch apart in each direction. It has been found that a suitable ceramic composition for the elements 20 comprises an alumina porcelain which includes approximately A1 0 in its composition. Such a porcelain has a hardness on the Moh scale which is close to 9 (or approximately 75 Rockwell), and a satisfactory porcelain of this type is manufactured by Coors Porcelain Co., Golden, Colo. under the tradename AD-85. Such a porcelain composition has a maximum temperature resistivity of approximately 1400 C. Other characteristics of such a porcelain include a tensile strength of approximately 18,000 p.s.i. at 70 F., and its modulus of elasticity is approximately 33x10 p.s.i.

The individual ceramic elements can be adhered to the neoprene elastomeric sleeve means 14 by any suitable adhesive or bonding means. A known bonding agent is produced by Coors Porcelain Co. of Golden, Colo., and the particular choice of bonding agent is not a part of the present invention. Likewise, the drill collar 10 can be attached, adhered, or otherwise fastened, to the pipe string 12 in any suitable manner, and it is known to utilize adhesives as well as mechanical fastening devices for fixing the position of a drill collar relative to a drill string or a pipe section upon which it is mounted. The drill collar 10 may be formed in halves or segments which can be placed around a drill string and fastened thereto by bands or straps, or other devices, which will maintain the drill collar in a tight and fixed position relative to the drill string. In the example which is being described with reference to FIGURE 1, the elastomeric sleeve means 14 may be formed as an integral structure from a neoprene composition having a hardness within the range of 60 to 70 Shore A durometer. This degree of hardness gives the elastomeric sleeve sufficient resiliency to absorb shocks which are imparted to the outside surface of the drill collar, and also the entire drill collar is sufliciently flexible to permit normal flexing of the drill string without setting up any stress points on the drill string.

Of course, it is to be understood that the above example is only representative of one drill collar product which can be made in accordance with the present invention. Various compositions of porcelain, having the indicated properties of hardness and heat resistance may be substituted, and the elastomeric sleeve means may be formed from other rubber or rubber-like compounds. Likewise, the ceramic elements may be positioned in or on the drill collar exterior surface in various patterns and in various ways, and the mosaic pattern which is illustrated in FIGURE 1 is only one example of a placement of a large number of ceramic elements or chips on or near the surface of a drill collar construction. Also, the drill collar 10 may be constructed in different shapes and sizes to meet particular drilling operation requirements.

Variations in this invention will become obvious to those skilled in this art, and all obvious and equivalent variations are intended to be included within the scope of the invention.

What is claimed is:

1. An improved drill collar for protecting a drill string, from shock and abrasion in an earth bore, comprising:

an elastomeric Sleeve means which can be adhered or affixed to a portion of the drill string which is to be protected, and

a plurality of closely spaced ceramic elements made of a porcelain composition and positioned to have portions exposed on an exterior surface of said elastomeric sleeve means so as to provide an abrasion-resistant surface on said elastomeric sleeve means, whereby said drill collar functions to absorb shocks and to resist abrasion and heat which otherwise would be imparted to the drill string in earth boring operations.

2. The improved drill collar of claim 1 wherein said elastomeric sleeve is adhered to the drill string by a bonding agent which fixes the position of said drill collar relative to a portion of the drill string.

3. The improved drill collar of claim 1 wherein said ceramic elements are adhesively bonded to the exterior surface of said elastomeri-c sleeve means.

4. The improvement of claim 1 wherein said porcelain composition comprises approximately 85% A1 5. The improvement of claim 1 wherein said ceramic elements are embedded into the exterior surface of said elastomeric sleeve means.

6. The improvement of claim 5 wherein at least the exposed portion of each of said ceramic elements is of a substantially hemispherical configuration, and wherein each said ceramic element is embedded in said elastomeric sleeve means so as to present a curved surface towards the outside surface of said elastomeric sleeve means.

7. The improvement of claim 5 wherein each of said ceramic elements includes a rounded or spherical surface portion which is directed radially outwardly away from the central axis of said drill collar.

8. The improvement of claim 1 wherein said elastomeric sleeve has a hardness within the range of to durometer.

9. The improvement of claim 8 wherein said elastomeric sleeve consists of a neoprene rubber composition.

References Cited UNITED STATES PATENTS 2,651,199 9/1953 Collins et al 308-4 X 2,690,934 10/ 1954 Holcombe 308--4 2,863,704 12/ 1958 Hillman 166176 X 3,054,647 9/ 1962 Von Rosenberg 3084 3,103,391 9/1963 Leathers 308-4 3,148,004 9/1964 Hall et al. 3084 3,268,274 8/1966 Ortlolf et al. 308--4 3,320,004 5/1967 Garrett 3084 3,343,890 9/1967 Homer 308-4 DAVID H. BROWN, Primary Examiner US. Cl. X.R. 3084 

